Float valve

Abstract

A float valve is mounted within the ullage of a liquid storage tank and is fitted to a lower end of a vapour vent line. The float valve includes a generally tubular vent body having an opening arrangement which allows vapour to escape from the tank into the vent line, and a float assembly which undergoes damped upward movement in response to the liquid level within the tank exceeding a threshold level. The float assembly comprises a sleeve and a float arrangement separated from each other by an adjustable distance. In this way, the volume of liquid required in the tank to make the float assembly move upward can be changed. The float valve may include a relief valve or a plug with a bleed orifice to permit vapour flow from the tank to the vapour vent line in the event that the pressure within the tank exceeds a predetermined value.

1 . A float valve for controlling a vent line from a liquid storage tank, the float valve comprising an elongate float assembly movable on a tubular vent body, wherein upward movement of the float assembly is damped by pressure of vapour within the tubular body, at least just prior to the valve closing onto its seat, and wherein the float assembly comprises a sleeve, a float arrangement and means for adjusting a position of the float arrangement relative to the sleeve. 
   
   
       2 . A float valve according to  claim 1 , wherein the vent body comprises a relief valve arranged to open in response to the pressure inside the tank passes a predetermined threshold level. 
   
   
       3 . A float valve according to  claim 2 , wherein the predetermined threshold level is adjustable. 
   
   
       4 . A float valve according to  claim 1 , wherein the vent body comprises a plug having a bleed orifice. 
   
   
       5 . A float valve according to  claim 1 , wherein the float assembly comprises an elongate shaft disposed between the sleeve and the float arrangement. 
   
   
       6 . A float valve according to  claim 5 , wherein the elongate shaft is longer than the sleeve. 
   
   
       7 . A float valve according to  claim 5 , wherein the elongate shaft is at least twice as long as the sleeve portion. 
   
   
       8 . A float valve according to claim  5 , wherein the elongate shaft comprises indicia indicative of a volume of liquid within the tank. 
   
   
       9 . A float valve according to  claim 1 , wherein the float arrangement comprises a closed-cell polyvinyl chloride body. 
   
   
       10 . A float valve according to  claim 1 , wherein the vent body comprises an opening arrangement having a triangularly shaped aperture arranged to allow vapour exchange between the interior of the tank and the vent line. 
   
   
       11 . A float valve according to  claim 5 , wherein the float arrangement is slidable along the elongate shaft. 
   
   
       12 . A float valve according to  claim 1 , wherein the float valve is configured to transition from an open to a closed state progressively in response to a small increase in the volume of liquid within the tank. 
   
   
       13 . A float valve according to  claim 12 , wherein the small increase in the volume corresponds to about a 1% increase in the volume of liquid within the tank 
   
   
       14 . A float assembly for use in a float valve according to  claim 1 , the float assembly comprising a sleeve, a float arrangement and means for adjusting a position of the float arrangement relative to the sleeve. 
   
   
       15 . An externally installable relief cartridge for use in a float valve according to  claim 1 , whereby, when installed, at least a part of the relief cartridge is provided externally of the vent body, between the vent body and the sleeve. 
   
   
       16 . An external relief cartridge according to  claim 15 , wherein the relief valve comprises a pressure or vacuum relief valve. 
   
   
       17 . A method of installing a float valve according to  claim 1 , the method comprising providing the valve so as to be in communication with a vent line from a liquid storage tank and adjusting a position of the float arrangement relative to the sleeve. 
   
   
       18 . A method according to  claim 17 , comprising sliding the float arrangement along the elongate shaft. 
   
   
       19 . A method according to  claim 17 , comprising adjusting the position of the float arrangement on the basis of indicia on the elongate shaft, indicative of a volume of liquid within the tank. 
   
   
       20 . (canceled)